1. Field of the Invention
The present invention generally relates to a printer with a line head. More specifically, the present invention relates to a so-called page printer in which a photosensitive member is exposed by a line head having a large number of light points aligned in a direction of a print line.
2. Description of the Prior Art
In a conventional laser beam printer, an electrophotographing system having a laser scanner unit is utilized for an exposing means for exposing a photosensitive member. In such a laser beam printer, a laser beam is scanned on a surface of a photosensitive drum in a direction parallel to a rotation axis of the photosensitive drum (a main scanning direction) while the photosensitive drum is rotated in an auxiliary scanning direction, whereby an electrostatic latent image is formed on the photosensitive drum.
On the other hand, according to the recent advancement of semiconductor technology, heads such as an LED head, a fluorescent head, a liquid crystal head, and etc., forming a line head having a large number of light points aligned over a whole width of the photosensitive drum have been developed, and a page printer which utilizes such as a line head as the exposing means has been put into practical use. Such a page printer can be obtained with a low cost and can be miniaturized in comparison with the above described laser beam printer.
However, in such a multi-point type page printer, because light from an adjacent light point is wrapped around to a pixel or dot not to be exposed, an image is blurred in the auxiliary scanning direction since due to the irregularity of the rotation of the photosensitive drum, a dot becomes to be thinned or fatted. In general, in an inverted developing system, i.e., a system in which a background portion is exposed and an image portion is not exposed, the dot or pixel is thinned, and in a non-inverted developing system, i.e., a system in which the image portion is exposed and the background portion is not exposed, the dot or pixel is fatted. Therefore, in the conventional page printer, due to the thinning or fatting of the dot or pixel, i.e., a line width, an image quality or print quality is low.